Change the Base order ID of the spell and it'll work.
@ludnica
For me the same thing happen (yes, I change the order ID), but I don't test it with storm bolt.
Using 2 ability of same type in one hero don't work =.='
@95blojoe
He say the Text - Order String - Use/Turn off
Every Data in spell is part of stats of the spell
Order string is not the same thing as data id, unless NewGen makes the changing of normal spells' data ids to be changed. I am not familiar with NewGen. However, only Spellbook and Channel and another ability (I forgot its name) have changeable data ids. So, as long you put two custom spells that are based on the same ability (and that ability is not one of those 3 I listed), you will always have trouble, no matter what you change .